Incontinence Quality of Life Questionnaire

The I-QOL measure is used in patients with chronic urinary incontinence (i.e., urge, stress, and mixed) to assess the impact of incontinence on quality of life.^30,31 The I-QOL is a 22-item scale consisting of three domains: avoidance and limiting behaviour (eight items), psychosocial impacts (nine items), and social embarrassment (five items).³¹ Each item is scored according to a five-point scale (1 = extremely and 5 = not at all).²⁸ Scores (range: 0 to 100) are calculated for each domain along with an overall composite score for the 22 items. The higher the I-QOL score, the higher the quality of life and the lower the impact of incontinence on health-related quality of life (HRQoL).^28,31 The I-QOL items have been shown to be internally consistent (overall Cronbach’s alpha = 0.95, subscales: 0.87 to 0.93), with a high test–retest reliability (overall r = 0.93 after 18 days).²⁸ Construct validity (as demonstrated by discriminant and convergent validity) and responsiveness (e.g., ability to discriminate between perceived levels of severity) were considered acceptable.²⁸ The I-QOL has been translated into many languages, but only psychometrically validated in French, Spanish, Swedish, and German.²⁸ No MCID has been reported for non-stress incontinence, while the between-treatment MCID for the total I-QOL score in stress incontinence has been reported to be 2.5 points.³²

King’s Health Questionnaire

The standard version of the KHQ is a 21-item disease-specific questionnaire that has been developed and validated for participants with urinary incontinence.²⁷ The KHQ consists of nine domains: general health perceptions, impact on life, role limitations, physical limitations, social limitations, personal relationships, emotions, sleep and energy, and incontinence severity measures. Item scores are converted to a standardized scale. Scores for each domain range from 0 to 100, where 0 indicates the best outcome or response and 100 indicates the worst outcome or response.²⁷

KHQ was validated in a study of 24 patients with overactive bladder (OAB)⁴⁴ in the US, and Reese et al.⁴⁵ evaluated the psychometric properties of the KHQ in 1,284 patients with OAB. Reese et al. concluded that psychometric testing supports the reliability and validity of the KHQ as an OAB-specific measure of HRQoL.⁴⁵ Statistically significant correlations between KHQ and patient-reported OAB symptoms such as urge-incontinence episodes (median percentage change) were also observed in patients after 12 weeks of treatment with tolterodine (r = 0.16 to 0.32, P ≤ 0.0011).⁴⁶ A within-group MCID of 5 points has been reported for each domain in patients with overactive bladder.^28,29

Twelve-Item Short-Form Health Survey

In response to demand for a reduction in responder and research administrative burden, the SF-12, a shortened derivative of the SF-36,^33,34 was created.⁴⁷

The SF-36 is a 36-item, general health status instrument that has been used extensively in clinical trials in many disease areas.⁴⁸ It consists of eight health domains: physical functioning, role — physical, bodily pain, general health, vitality, social functioning, role — emotional, and mental health.⁴⁷ For each of the eight domains, a subscale score can be calculated. The SF-36 provides two component summaries: the physical component summary (PCS) and the mental component summary (MCS). The PCS and MCS scores range from 0 to 100, with higher scores indicating better health status. The summary scales are scored using norm-based methods, with regression weights and constants derived from the general US population. Both the PCS and MCS scales are transformed to have a mean of 50 and a standard deviation of 10 in the general US population. Therefore, all scores above or below 50 are considered above or below average for the general US population.⁴⁷

By comparison, the SF-12 consists of 12 items from the SF-36 that are scored and weighted to obtain two summary scores: one for physical health (PCS) and one for mental health (MCS).^33,34 More than 90% of the variance in the SF-36 PCS and SF-36 MCS is captured by the items in the SF-12.³⁴ The SF-12 summary scores have been reported to be both psychometrically sound and good predictors of the original SF-36 scores.³³ Trading off quantity of data for increased practicality, the SF-12 is expected to be of value in studies with large sample sizes in which the objective is to survey changes in physical and mental health outcomes.⁴⁷ No published MCIDs could be found, however, for the SF-12 (or SF-36) for OAB or urinary incontinence.

European Quality of Life Five Dimensions Questionnaire

The EQ-5D is a generic quality of life instrument that may be applied to a wide range of health conditions and treatments.^49,50 The first of two parts of the EQ-5D is a descriptive system that classifies respondents (aged 12 years or older) into one of 243 distinct health states. The descriptive system consists of the following five dimensions: mobility, self-care, usual activities, pain or discomfort, and anxiety or depression. Each dimension has three possible levels (1, 2, or 3) representing “no problems,” “some problems,” and “extreme problems,” respectively. Respondents are asked to choose the level that reflects their health state for each of the five dimensions. A scoring function can be used to assign a value (EQ-5D index score) to self-reported health states from a set of population-based preference weights.^49,50 The second part is a 20 cm visual analog scale (EQ-VAS) that has end points labelled 0 and 100, with respective anchors of “worst imaginable health state” and “best imaginable health state.” Respondents are asked to rate their health by drawing a line from an anchor box to the point on the EQ-VAS that best represents their health on that day. Hence, the EQ-5D produces three types of data for each respondent:

1. A profile indicating the extent of problems on each of the five dimensions represented by a five-digit descriptor, such as 11121, 33211, etc.
2. A population preference-weighted health index score based on the descriptive system
3. A self-reported assessment of health status based on the EQ-VAS.

The EQ-5D index score is generated by applying a multi-attribute utility function to the descriptive system. Different utility functions are available that reflect the preferences of specific populations (e.g., US or UK). The lowest possible overall score (corresponding to severe problems on all five attributes) varies depending on the utility function that is applied to the descriptive system (e.g., −0.59 for the UK algorithm and −0.109 for the US algorithm). Scores less than 0 represent health states that are valued by society as being worse than dead, while scores of 0 and 1.00 are assigned to the health states “dead” and “perfect health,” respectively. Reported MCIDs for this scale have ranged from 0.033 to 0.074.⁵¹

In a physiotherapy study of women with urinary incontinence,⁵² the EQ-5D was found to be inadequate for discriminating changes in health utility between multiple groups as a function of treatment and, thus, was not recommended by the authors for evaluating female urinary incontinence. However, in a subsequently published narrative review of the evidence (n = 17 studies; 48 to 9,487 patients per study; age of patients: 50 to 67 years) for the use of the EQ-5D in patients with urinary incontinence or complaints,⁵³ in which the previous study⁵² was included (and criticized), the EQ-5D was found to be generally useful in the population overall, performing adequately on measures of construct validity, responsiveness, and reliability when compared with disease-specific instruments such as the I-QOL and KHQ. However, a limitation of this review was that it did not specifically examine content validity and so cannot say with certainty whether the EQ-5D adequately captures utility around incontinence indirectly through its existing dimensions.⁵³ No published MCIDs could be found for OAB or urinary incontinence for the EQ-5D.